Objective: The proposed research aims to build knowledge about four behavior disorders: depression, schizophreniform, antisocial, and substance abuse disorders. In all four disorders, developmental subtypes have been proposed as a way forward to carve up the heterogeneity now hindering scientific understanding. We will study heterogeneity within each disorder over the first three decades of life, by analyzing variation in onset (early versus later) and subsequent course (persistent, recurrent, or limited). We aim to ascertain the existence, discriminant validity, and implications of developmental subgroups within disorders. Methods: The Dunedin Study has traced the development of a representative 1972 birth cohort of 1,000 New Zealand men and women at birth and ages 3, 5, 7, 9, 11, 13, 15, 18, 21, and 26. New data will be gathered at age 31. Psychiatric data from childhood to age 31 will be analyzed to identify developmental subgroups within each disorder. Hypotheses address: (a) different childhood risk factors and family psychiatric histories for developmental subgroups, (b) different adult outcomes in work life, family life, and physical health for developmental subgroups, (c) proximal life events that precipitate adult-onset disorder, (d) temporal comorbid sequences in which one type of disorder reliably leads to another, and (f) whether findings apply to men and women, or if sex-specific models are needed. Implications for diagnosis: Findings will improve the current DSM classification system by enabling clinicians to use developmental history to know more about a disorder's probable etiology and prognosis. Implications for prevention: Findings will (a) yield recommendations for tailoring interventions to fit developmental subtypes, (b) clarify the relative importance of preventing onset versus recurrence, (c) identify factors posing pervasive risk for many disorders as top prevention priorities, (d) point to common sequences of disorders, which suggest that treatment of disorder A may prevent disorder B. Implications for genetic and neuroscience research: Findings will characterize psychiatric phenotypes more precisely, and show which subtypes have familial and neuro-developmental correlates.